1. Field of the Invention
The present invention relates to an automotive alternator and particularly relates to a rectifier cooling construction.
2. Description of the Related Art
In conventional automotive alternators, positive-side unidirectional conducting elements and negative-side unidirectional conducting elements have been supported by a positive-side cooling plate and a negative-side cooling plate so as to be positioned approximately in a common plane that is perpendicular to a rotating shaft, cooling fins have been formed so as to project from an opposite side of a first cooling plate from the side on which the unidirectional conducting elements are supported, and a second cooling plate has been fixed to a casing member, such that the cooling fins have been cooled by a cooling fan (see Patent Literature 1, for example).
Patent Literature 1: Japanese Patent No. 13342978 (Gazette)
In conventional automotive alternators, because the positive-side cooling plate and the negative-side cooling plate have been disposed so as to line up radially, the following problems have arisen, preventing effective cooling of rectifying apparatuses:
First, cooling airflows that have been sucked in through ventilating apertures due to rotation of the cooling fan reach the cooling fan through gaps between the positive-side cooling plate and the negative-side cooling plate and gaps between the cooling plate that is positioned inside and a bearing box. Sufficient cross-sectional area cannot be ensured in the gaps at these two positions as air channels through which the cooling airflows may pass, giving rise to pressure loss due to reductions in air channel cross-sectional area as the cooling airflows flow in.
Cooling airflow flow channels that extend from the ventilating apertures to the cooling fan are also divided by the positive-side cooling plate and the negative-side cooling plate. Thus, portions of the cooling airflows are discharged externally without passing through the cooling fins, reducing the volume of cooling airflow that passes through the cooling fins compared to the intake and discharge capacity of the cooling fan.
Because installation space for the cooling plate on the inside is also narrower, the number of cooling fins must be reduced, reducing heat radiating area.